Monday, 8 February 2010

A LEADING British government scientist has warned the United Nations’ climate panel to tackle its blunders or lose all credibility.

Robert Watson, chief scientist at Defra, the environment ministry, who chaired the Intergovernmental Panel on Climate Change (IPCC) from 1997 to 2002, was speaking after more potential inaccuracies emerged in the IPCC’s 2007 benchmark report on global warming.

The most important is a claim that global warming could cut rain-fed north African crop production by up to 50% by 2020, a remarkably short time for such a dramatic change. The claim has been quoted in speeches by Rajendra Pachauri, the IPCC chairman, and by Ban Ki-moon, the UN secretary-general.

This weekend Professor Chris Field, the new lead author of the IPCC’s climate impacts team, told The Sunday Times that he could find nothing in the report to support the claim. The revelation follows the IPCC’s retraction of a claim that the Himalayan glaciers might all melt by 2035.

This report is the IPCC’s most politically sensitive publication, distilling its most important science into a form accessible to politicians and policy makers. Its lead authors include Pachauri himself.

In it he wrote: “By 2020, in some countries, yields from rain-fed agriculture could be reduced by up to 50%. Agricultural production, including access to food, in many African countries is projected to be severely compromised.” The same claims have since been cited in speeches to world leaders by Pachauri and Ban.

Speaking at the 2008 global climate talks in Poznan, Poland, Pachauri said: “In some countries of Africa, yields from rain-fed agriculture could be reduced by 50% by 2020.” In a speech last July, Ban said: “Yields from rain-fed agriculture could fall by half in some African countries over the next 10 years.”

Speaking this weekend, Field said: “I was not an author on the Synthesis Report but on reading it I cannot find support for the statement about African crop yield declines.”

Watson said such claims should be based on hard evidence. “Any such projection should be based on peer-reviewed literature from computer modelling of how agricultural yields would respond to climate change. I can see no such data supporting the IPCC report,” he said.

The claims in the Synthesis Report go back to the IPCC’s report on the global impacts of climate change. It warns that all Africa faces a long-term threat from farmland turning to desert and then says of north Africa, “additional risks that could be exacerbated by climate change include greater erosion, deficiencies in yields from rain-fed agriculture of up to 50% during the 2000-20 period, and reductions in crop growth period (Agoumi, 2003)”.

“Agoumi” refers to a 2003 policy paper written for the International Institute for Sustainable Development, a Canadian think tank. The paper was not peer-reviewed.

Its author was Professor Ali Agoumi, a Moroccan climate expert who looked at the potential impacts of climate change on Tunisia, Morocco and Algeria. His report refers to the risk of “deficient yields from rain-based agriculture of up to 50% during the 2000–20 period”.

These claims refer to other reports prepared by civil servants in each of the three countries as submissions to the UN. These do not appear to have been peer-reviewed either.

The IPCC is also facing criticism over its reports on how sea level rise might affect Holland. Dutch ministers have demanded that it correct a claim that more than half of the Netherlands lies below sea level when, in reality, it is about a quarter.

The errors seem likely to bring about change at the IPCC. Field said: “The IPCC needs to investigate a more sophisticated approach for dealing with emerging errors.”

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